hi cosmo-torun,
We have just two and a half days left to propose a cosmology hands-on project for the proposed TCfA visiting centre. IMHO a mirror-lined dodecahedron is a relatively easy to construct possibility and gives visitors something of a concrete intuitive example of a multiply connected space (despite the problems in the analogy):
Please update the wiki directly: http://cosmo.torun.pl/foswiki/bin/view/Cosmo/TCfAVisitingCentre
pozdr boud